With an electric cable consisting of individual conductors enclosed by a common insulating hose, the following problem is known to arise. If the cable is used in a damp environment, the moisture can penetrate into it from one or both ends, or at a point where the insulating hose is damaged. This moisture can then reach as far as the electrical contacting elements, which generally causes a fault in a connected electrical device.
In order that the moisture may be prevented from reaching the electrical contacting elements, there are known techniques for sealing one or both final sections of the cable with a pourable sealing compound. One possible technique consists of the introduction of the pourable sealing compound into the relevant cable end until it rises to the top of the insulating hose because it has set at an undefined point inside. An improved technique is to attach a masticated caoutchouc mass as a preseal round a bundle of conductors at a predetermined distance from their free ends before the final fitting of the insulating hose. The insulating hose is then pulled far enough over the caoutchouc mass to form a final cable section which can be filled with a pourable sealing compound. These known methods, however, involve either the use of a large amount of sealing material or a process which is unacceptably time-consuming. With regard to the last-mentioned method, it must also be said that, because the presealing caoutchouc mass is placed first and the insulating hose only pulled over it afterwards, it cannot be guaranteed that the sealing mass fills out the entire diameter of the insulating hose. This means that pourable sealing compound can pass the presealing mass.
In addition, a process of sealing an electric cable has been publicized in DE 37 05 958 C1 whereby, in order to minimize expenditure of work and material, the presealing is effected by a relatively fast-hardening sealing compound--e.g. polyurethane foam--which is injected into the cable from the relevant end above a point where it is being compressed by means of a device. This method, however, also has disadvantages. On the one hand, the conductors can be damaged by the compression device, while, on the other, ugly and unwanted marking of the insulating hose can hardly be avoided.